Process of manufacturing aluminum alloy workpiece

ABSTRACT

A process of manufacturing an aluminum alloy workpiece includes a preparation step, in which an aluminum alloy sheet, a forming die, and a handling device are prepared; an aging and forming step including a heating substep for heating the aluminum alloy sheet to a first temperature, a transferring substep for transferring the aluminum alloy sheet to the die at a second temperature, and a forming and cooling substep for forming the aluminum alloy sheet into a target shape; and an aging out of forming die step, in which the formed aluminum alloy sheet is removed from the die, is heated to a third temperature, and undergoes another aging treatment to manufacture the aluminum alloy workpiece.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of Taiwanese Invention PatentApplication No. 110143561, filed on Nov. 23, 2021.

FIELD

The disclosure relates to a process of manufacturing alloy workpieces,especially with regard to a process of manufacturing an aluminum alloyworkpiece.

BACKGROUND

Since aluminum alloy has the characteristics of improved formabilityafter heating, a process with specific forming temperature can be usedto form the specific type of aluminum alloy workpieces and achievedesired shape. According to the heating temperature, can be divided intotwo forming processes: warm forming and hot forming. In the warm formingprocess, the aluminum alloy sheet is heated to a temperature above 100°C. but below the recrystallization temperature, after that, it is sentinto the die for forming and cooling. In the hot forming process, thealuminum alloy sheet is first heated to the solid solution temperaturefor solution heat treatment, then it is sent into the die for formingand quenching. Subsequently, the formed aluminum alloy sheet mustundergo an artificial aging treatment after removing from the formingdie to achieve the target strength.

However, the subsequent aging treatment in the hot forming process takesa considerable amount of operating time, therefore increasing theproduction cost and energy consumption of the hot forming process.Moreover, the hot forming die continues to work under the condition ofrepeated high temperature and rapid cooling. The service life is thusshortened and the production cost of the hot forming process isincreased.

SUMMARY

Therefore, an object of the present disclosure is to provide a processof manufacturing an aluminum alloy workpiece which can conquer at leastone of the disadvantages of the previous process.

A preparation step, an aging and forming step, and an aging out offorming die step are included in the process of manufacturing analuminum alloy workpiece according to this disclosure.

An aluminum alloy sheet, a forming die, and a handling device areprepared in the preparation step. A transfer mechanism for at least onedegree of freedom movement and a dismountable temperature control moduleconnected to the transfer mechanism are included in the handling device.The dismountable temperature control module has a second temperature.

The aging and forming step includes a heating substep, a transferringsubstep, and a forming and cooling substep.

In the heating substep, the aluminum alloy sheet is heated to a firsttemperature lower than a solid solution temperature but higher than asolid solution temperature of a Guinier-Preston Zone (G-P zone), and isthen transferred to the temperature control module.

In the transferring substep, the transfer mechanism is used fortransferring the aluminum alloy sheet contained in the temperaturecontrol module into the forming die. The aluminum alloy sheet ismaintained at the second temperature through the temperature controlmodule. The second temperature is lower than the solid solutiontemperature but higher than the solid solution temperature of the G-Pzone. In the forming and cooling substep, the aluminum alloy sheet isformed into a target shape while cooling in the forming die.

In the aging out of forming die step, the formed aluminum alloy sheet isremoved from the forming die and is heated to a third temperature thatis lower than the solid solution temperature but higher than the solidsolution temperature of the G-P zone, and then undergoes another agingtreatment to manufacture the aluminum alloy workpiece.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present disclosure are apparentwith detailed description and figures of the embodiments:

FIG. 1 is a flow chart, illustrating the steps involved in a process ofmanufacturing an aluminum alloy workpiece according to the firstembodiment of the present disclosure;

FIG. 2 is a perspective view of a handling device used in an aging andforming step of the first embodiment;

FIG. 3 is a graph of temperature versus time, illustrating a temperaturechange of treating an aluminum alloy sheet with the process of the firstembodiment;

FIG. 4 is a flow chart, illustrating the steps involved in a process ofmanufacturing an aluminum alloy workpiece according to the secondembodiment of the present disclosure;

FIG. 5 is a graph of temperature versus time, illustrating a temperaturechange of treating an aluminum alloy sheet with the process of thesecond embodiment; and

FIG. 6 is a schematic top view, illustrating a layout of apre-processing substep in a preparation step and a heating substep of anaging and forming step of the second embodiment.

DETAILED DESCRIPTION

It should be noted that similar elements are denoted by the samereference numerals throughout the disclosure before describing thepresent disclosure in more detail with reference to the figures andembodiments.

Referring to FIG. 1 , a process of manufacturing an aluminum alloyworkpiece according to the first embodiment of the present disclosureincludes a preparation step 11, an aging and forming step 12, and anaging out of forming die step 13.

Referring to FIGS. 1 and 2 , an aluminum alloy sheet (not shown), aforming die (not shown), and a handling device 2 are prepared in thepreparation step 11.

A transfer mechanism 21 for at least one degree of freedom movement anda dismountable temperature control module 22 are included in thehandling device 2. The transfer mechanism 21 includes a robotic arm 29for detachable connection with the temperature control module 22.

The aluminum alloy sheet in the first embodiment is the AA 7075 aluminumalloy sheet with required pre-aging treatment. Furthermore, the aluminumalloy sheet is manufactured into an automotive stamping part as anexample for the first embodiment. The transfer mechanism 21 and thetemperature control module 22 can be connected to or separated from eachother through a programmable logic control to arrange the layout ofautomated operations.

Referring to FIGS. 1 to 3 , the aging and forming step 12 includes aheating substep 121, a transferring substep 122, and a forming andcooling substep 123. In the heating substep 121, the aluminum alloysheet is heated in a heating station to a first temperature lower than asolid solution temperature (T1) but higher than a solid solutiontemperature (T2) of a Guinier-Preston Zone (G-P zone) at a rate of morethan 10° C. per second. Then, it is transferred to the temperaturecontrol module 22 of the handling device 2.

The aluminum alloy sheet is held in the heating station for a period oftime at the first temperature to achieve a uniform temperaturedistribution and also to carry out the first aging treatment.Specifically, the first temperature is 130 to 270° C. if it is the 6000series of aluminum alloy sheet; and, the heating temperature is 150 to250° C. if it is the 7000 series of aluminum alloy sheet.

The AA 7075 aluminum alloy sheet of AA 7000 series aluminum alloy istaken as an example to illustrate in this embodiment, so the firsttemperature is set at 200° C. It is worth noting that the holding timeof the first temperature is preferably to be chosen as two minutes,which is sufficient for the aluminum alloy sheet to reach a uniformtemperature distribution and prepare required heat energy for thesubsequent aging treatment. Especially, a strengthening phase of thealuminum alloy sheet is started precipitating and a metastable state isinitially reached when the heating temperature is maintained above thesolid solution temperature (T2) of the G-P zone.

In the transferring substep 122, the aluminum alloy sheet contained inthe temperature control module 22 is transferred through the robotic arm29 of the transfer mechanism 21 to the forming die within a transporttime. The temperature control module 22 has a second temperature.

The aluminum alloy sheet is maintained at the second temperature in thetemperature control module 22. The second temperature is lower than thesolid solution temperature (T1) but higher than the solid solutiontemperature (T2) of the G-P zone.

The sum of the holding time of the first temperature and the transporttime is 5 to 300 seconds to transfer the aluminum alloy sheet into theforming die as soon as possible to prevent the temperature of thealuminum alloy sheet from dropping. A certain formability of thealuminum alloy sheet is ensured when transferring into the forming dieand thus the quality of the formed part is optimized. It is noteworthythat the forming die has to be clamped immediately after transferringthe aluminum alloy sheet into the forming die to prevent the temperatureof the aluminum alloy sheet from dropping after leaving the temperaturecontrol module 22.

In the forming and cooling substep 123, the aluminum alloy sheet is heldin the forming die for more than 5 seconds to be formed into a desiredshape under condition of improved formability, and the aluminum alloysheet is formed into a target shape while cooling in the forming die.That is, in the forming and cooling substep 123, an aluminum alloy plateis formed during the aging process.

In the aging out of forming die step 13, the formed part is removed fromthe forming die and is heated in another heating station to a thirdtemperature, which is lower than the solid solution temperature (T1) buthigher than the solid solution temperature (T2) of the G-P zone. Thealuminum alloy workpiece is manufactured after aging treated again. Thethird temperature is 170 to 190° C.

To be specific, the aging out of forming die step 13 is preferable to gowith a paint bake process since the aluminum alloy sheet is manufacturedto be an automotive stamping part in this embodiment.

The temperature and the holding time are set to be 185° C. and 20minutes, respectively, for the second aging treatment, which can bematched with the parameters of the paint bake process.

Besides the advantage of being aging treated again through the paintbake process, the automotive stamping part can also achieve a peakstrength and obtain a strengthening phase after the paint bake process.The strength loss of the automotive stamping part due to the paint bakeprocess is avoided. Therefore, the strength of the aluminum alloyworkpiece is maintained at a peak state after the paint bake process andthe aging treatment and the heating process are coordinated through themanufacture process of the first embodiment.

Not only the thermal energy of the paint bake process is properlyutilized, the thermal energy consumption is also reduced dramaticallycompared with the existing heat treatment with parameters of heating to120° C. and holding for 24 hours.

Furthermore, thermal accumulation of the forming die because of frequentcontact with heated sheets or mass production is reduced due to lowertarget forming temperature. The forming die life is effectivelyincreased and the production cost is thus reduced.

Referring to FIGS. 4 and 5 , a process of manufacturing an aluminumalloy workpiece according to the second embodiment of the presentdisclosure is shown, which is similar with the first embodiment.

The difference between the first and second embodiments is that theprepared aluminum alloy sheet in the preparation step 11 of the secondembodiment is untreated (F state), and a pre-processing substep 111 isthus concluded in the preparation step 11. In the pre-processing substep111, the aluminum alloy sheet is heated to the solid solutiontemperature (T1) and is held for a period of time, and is then quenched.Additionally, the aluminum alloy sheet requires further heat treatmentin the heating substep 121 to ensure the strength after the entiremanufacture process due to not being heat treated compared with thefirst embodiment. Therefore, the aluminum alloy sheet is slowly heatedto the first temperature for 20 minutes, and is then held for 5 minutes.

In addition, the overall holding time and transfer time at the firsttemperature is 5 to 20 minutes since it does not take too much time totransfer the aluminum alloy sheet contained in the temperature controlmodule 22 into the forming die. The second embodiment mainly processesthe aluminum alloy sheet that is not being heat treated. The heatingsubstep 121 is preferably conducted in 30 minutes after thepre-processing step 111.

Relative slower heating and longer holding time are required in theheating substep 121 to ensure that the aluminum alloy sheet iscompletely pre-aged before the forming and cooling substep 123. Besidesthe differences mentioned above, the effect of the first embodiment canbe achieved by the second embodiment.

Referring to FIG. 6 and FIG. 4 , a solid solution heating furnace zone(Z1) for conducting the pre-processing substep 111 and a warm-formingheating furnace zone (Z2) for conducting the heating substep 121 can beplaced respectively (see FIG. 6 ) if different aluminum alloy sheets areneeded to be manufactured separately by the first embodiment and thesecond embodiment at the same time.

Multiple handling devices 2 are arranged between the solid solutionheating furnace zone (Z1) and the warm-forming heating furnace zone (Z2)to achieve the configuration of production lines. The efficiency ofwhole manufacturing process is optimized and it is conducive to massproduction.

In summary, the aluminum alloy sheet is contained in the temperaturecontrol module 22 to maintain required aging treatment whiletransferring into the forming die through the handling device 2 bycombining heating process of the pre-aging treatment with transferprocess of the aluminum alloy sheet of this disclosure.

It not only solves the problem of dropping temperature during thetransfer process of heated aluminum alloy sheet, but also avoidconsumption of time by reheating process. Besides the improvedformability after heating is maintained and the quality of workpiece isoptimized, the aging treatment process of the aluminum alloy sheet canalso be flexibly arranged.

Furthermore, the forming and cooling processes are completed in theforming die at the same time, and the aging treatment can also beconducted by going with subsequent process, such as the paint bakeprocess.

The peak strength of the aluminum alloy sheet is achieved aftercompleting subsequent processes.

In addition to the prevented strength loss, it is beneficial forimproving production efficiency by reduced manufacturing time andefficiency costs. Therefore, the object of this disclosure can indeed beachieved.

In the description above, numerous specific details have been set forthin order to provide a thorough understanding of the embodiments for thepurposes of explanation.

However, it will be apparent to those one skilled in the art that one ormore other embodiments may be practiced without some of these specificdetails.

It should also be appreciated that reference throughout thisspecification to “one embodiment,” “an embodiment,” an embodiment withan indication of an ordinal number and so forth means that a particularfeature, structure, or characteristic may be included in the practice ofthe disclosure. It should be further appreciated that in thedescription, various features are sometimes grouped together in a singleembodiment, figure, or description thereof for the purpose ofstreamlining the disclosure and aiding in the understanding of variousinventive aspects, and that one or more features or specific detailsfrom one embodiment may be practiced together with one or more featuresor specific details from another embodiment, where appropriate, in thepractice of the disclosure.

While the disclosure has been described in connection with what areconsidered the exemplary embodiments, it is understood that thisdisclosure is not limited to the disclosed embodiments but is intendedto cover various arrangements included within the spirit and scope ofthe broadest interpretation so as to encompass all such modificationsand equivalent arrangements.

What is claimed is:
 1. A process of manufacturing an aluminum alloyworkpiece, comprising: a preparation step, in which an aluminum alloysheet, a forming die, and a handling device are prepared, the handlingdevice including a transfer mechanism for at least one degree of freedommovement, and a dismountable temperature control module detachablyconnected to the transfer mechanism, said dismountable temperaturecontrol module having a second temperature; an aging and forming stepincluding a heating substep, in which the aluminum alloy sheet is heatedto a first temperature lower than a solid solution temperature buthigher than a solid solution temperature of a Guinier-Preston Zone (G-Pzone), and is then transferred to the temperature control module, atransferring substep, in which the transfer mechanism is used fortransferring the aluminum alloy sheet contained in the temperaturecontrol module into the forming die, the aluminum alloy sheet beingmaintained at the second temperature through the temperature controlmodule, the second temperature being lower than the solid solutiontemperature but higher than the solid solution temperature of the G-Pzone, and a forming and cooling substep, in which the aluminum alloysheet is formed into a target shape while cooling in the forming die;and an aging out of forming die step, in which the formed aluminum sheetis removed from the forming die, is heated to a third temperature thatis lower than the solid solution temperature but higher than the solidsolution temperature of the G-P zone, and then undergoes another agingtreatment to manufacture the aluminum alloy workpiece.
 2. The process ofclaim 1, wherein, in the preparation step, the aluminum alloy sheet hasundergone a pre-aging treatment.
 3. The process of claim 2, wherein, inthe heating substep, the aluminum alloy sheet is heated to the firsttemperature at a rate of more than 10° C. per second.
 4. The process ofclaim 3, wherein: in the heating substep, the first temperature is heldfor a period of time; in the transferring substep, the aluminum alloysheet contained in the temperature control module is transferred intothe forming die within a transport time; and the sum of the holding timeof the first temperature and the transport time is 5 to 300 seconds. 5.The process of claim 1, wherein the preparation step includes apre-processing substep, in which the aluminum alloy sheet is heated tothe solid solution temperature for a period of time, followed byquenching.
 6. The process of claim 1, wherein, in the heating substep,the aluminum alloy sheet is heated to the first temperature within aperiod of 10 to 30 minutes.
 7. The process of claim 6, wherein: in theheating substep, the first temperature is held for a period of time; inthe transferring substep, the aluminum alloy sheet contained in thetemperature control module is transferred into the forming die within atransport time; and the sum of the holding time of the first temperatureand the transport time is 5 to 20 minutes.
 8. The process of claim 1,wherein, in the heating substep, the first temperature is 130 to 270° C.9. The process of claim 1, wherein, in the aging out of forming diestep, the third temperature is 170 to 190° C.
 10. The process of claim5, wherein the heating substep is conducted within 30 minutes after thepre-processing substep.